Opinions are only valuable where facts are not available. I can't have an "opinion" that London is the capital of Spain, for example, that's not an opinion, that's just plain wrong. The distinction between opinion and fact has become increasingly blurred.
I suppose you could say that so long as he's still on the air that he's doing his job. That's true in one sense. But when people spend their time listening to someone talk about sports, they are looking for an honest informed opinion and information, not whatever slop someone feels like slinging. If he doesn't like Brewster's optimism, he should suck it up and behave like a professional. It would please many in the local media if Brewster was to wear sackcloth and ashes, and reject any hope at a Rose Bowl, but that is not his job.